Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

Computers and devices

Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Network130.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
130.0.0.0
Broadcast address
131.255.255.255
First usable
130.0.0.1
Last usable
131.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
B (default /16)
As numbers
Hex 82000000 · Integer 2181038080 to 2214592511
Reverse DNS zones
130.in-addr.arpa
131.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000010.00000000.00000000.00000000130.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network10000010.00000000.00000000.00000000130.0.0.0
Broadcast10000011.11111111.11111111.11111111131.255.255.255
Split into smaller subnets/19
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

130.0.0.0/7 makes 4,096 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1130.0.0.0/19130.0.0.1 to 130.0.31.254130.0.31.2558,190
2130.0.32.0/19130.0.32.1 to 130.0.63.254130.0.63.2558,190
3130.0.64.0/19130.0.64.1 to 130.0.95.254130.0.95.2558,190
4130.0.96.0/19130.0.96.1 to 130.0.127.254130.0.127.2558,190
5130.0.128.0/19130.0.128.1 to 130.0.159.254130.0.159.2558,190
6130.0.160.0/19130.0.160.1 to 130.0.191.254130.0.191.2558,190
7130.0.192.0/19130.0.192.1 to 130.0.223.254130.0.223.2558,190
8130.0.224.0/19130.0.224.1 to 130.0.255.254130.0.255.2558,190
9130.1.0.0/19130.1.0.1 to 130.1.31.254130.1.31.2558,190
10130.1.32.0/19130.1.32.1 to 130.1.63.254130.1.63.2558,190
11130.1.64.0/19130.1.64.1 to 130.1.95.254130.1.95.2558,190
12130.1.96.0/19130.1.96.1 to 130.1.127.254130.1.127.2558,190
13130.1.128.0/19130.1.128.1 to 130.1.159.254130.1.159.2558,190
14130.1.160.0/19130.1.160.1 to 130.1.191.254130.1.191.2558,190
15130.1.192.0/19130.1.192.1 to 130.1.223.254130.1.223.2558,190
16130.1.224.0/19130.1.224.1 to 130.1.255.254130.1.255.2558,190
17130.2.0.0/19130.2.0.1 to 130.2.31.254130.2.31.2558,190
18130.2.32.0/19130.2.32.1 to 130.2.63.254130.2.63.2558,190
19130.2.64.0/19130.2.64.1 to 130.2.95.254130.2.95.2558,190
20130.2.96.0/19130.2.96.1 to 130.2.127.254130.2.127.2558,190
21130.2.128.0/19130.2.128.1 to 130.2.159.254130.2.159.2558,190
22130.2.160.0/19130.2.160.1 to 130.2.191.254130.2.191.2558,190
23130.2.192.0/19130.2.192.1 to 130.2.223.254130.2.223.2558,190
24130.2.224.0/19130.2.224.1 to 130.2.255.254130.2.255.2558,190
25130.3.0.0/19130.3.0.1 to 130.3.31.254130.3.31.2558,190
26130.3.32.0/19130.3.32.1 to 130.3.63.254130.3.63.2558,190
27130.3.64.0/19130.3.64.1 to 130.3.95.254130.3.95.2558,190
28130.3.96.0/19130.3.96.1 to 130.3.127.254130.3.127.2558,190
29130.3.128.0/19130.3.128.1 to 130.3.159.254130.3.159.2558,190
30130.3.160.0/19130.3.160.1 to 130.3.191.254130.3.191.2558,190
31130.3.192.0/19130.3.192.1 to 130.3.223.254130.3.223.2558,190
32130.3.224.0/19130.3.224.1 to 130.3.255.254130.3.255.2558,190
33130.4.0.0/19130.4.0.1 to 130.4.31.254130.4.31.2558,190
34130.4.32.0/19130.4.32.1 to 130.4.63.254130.4.63.2558,190
35130.4.64.0/19130.4.64.1 to 130.4.95.254130.4.95.2558,190
36130.4.96.0/19130.4.96.1 to 130.4.127.254130.4.127.2558,190
37130.4.128.0/19130.4.128.1 to 130.4.159.254130.4.159.2558,190
38130.4.160.0/19130.4.160.1 to 130.4.191.254130.4.191.2558,190
39130.4.192.0/19130.4.192.1 to 130.4.223.254130.4.223.2558,190
40130.4.224.0/19130.4.224.1 to 130.4.255.254130.4.255.2558,190
41130.5.0.0/19130.5.0.1 to 130.5.31.254130.5.31.2558,190
42130.5.32.0/19130.5.32.1 to 130.5.63.254130.5.63.2558,190
43130.5.64.0/19130.5.64.1 to 130.5.95.254130.5.95.2558,190
44130.5.96.0/19130.5.96.1 to 130.5.127.254130.5.127.2558,190
45130.5.128.0/19130.5.128.1 to 130.5.159.254130.5.159.2558,190
46130.5.160.0/19130.5.160.1 to 130.5.191.254130.5.191.2558,190
47130.5.192.0/19130.5.192.1 to 130.5.223.254130.5.223.2558,190
48130.5.224.0/19130.5.224.1 to 130.5.255.254130.5.255.2558,190
49130.6.0.0/19130.6.0.1 to 130.6.31.254130.6.31.2558,190
50130.6.32.0/19130.6.32.1 to 130.6.63.254130.6.63.2558,190
51130.6.64.0/19130.6.64.1 to 130.6.95.254130.6.95.2558,190
52130.6.96.0/19130.6.96.1 to 130.6.127.254130.6.127.2558,190
53130.6.128.0/19130.6.128.1 to 130.6.159.254130.6.159.2558,190
54130.6.160.0/19130.6.160.1 to 130.6.191.254130.6.191.2558,190
55130.6.192.0/19130.6.192.1 to 130.6.223.254130.6.223.2558,190
56130.6.224.0/19130.6.224.1 to 130.6.255.254130.6.255.2558,190
57130.7.0.0/19130.7.0.1 to 130.7.31.254130.7.31.2558,190
58130.7.32.0/19130.7.32.1 to 130.7.63.254130.7.63.2558,190
59130.7.64.0/19130.7.64.1 to 130.7.95.254130.7.95.2558,190
60130.7.96.0/19130.7.96.1 to 130.7.127.254130.7.127.2558,190
61130.7.128.0/19130.7.128.1 to 130.7.159.254130.7.159.2558,190
62130.7.160.0/19130.7.160.1 to 130.7.191.254130.7.191.2558,190
63130.7.192.0/19130.7.192.1 to 130.7.223.254130.7.223.2558,190
64130.7.224.0/19130.7.224.1 to 130.7.255.254130.7.255.2558,190
65130.8.0.0/19130.8.0.1 to 130.8.31.254130.8.31.2558,190
66130.8.32.0/19130.8.32.1 to 130.8.63.254130.8.63.2558,190
67130.8.64.0/19130.8.64.1 to 130.8.95.254130.8.95.2558,190
68130.8.96.0/19130.8.96.1 to 130.8.127.254130.8.127.2558,190
69130.8.128.0/19130.8.128.1 to 130.8.159.254130.8.159.2558,190
70130.8.160.0/19130.8.160.1 to 130.8.191.254130.8.191.2558,190
71130.8.192.0/19130.8.192.1 to 130.8.223.254130.8.223.2558,190
72130.8.224.0/19130.8.224.1 to 130.8.255.254130.8.255.2558,190
73130.9.0.0/19130.9.0.1 to 130.9.31.254130.9.31.2558,190
74130.9.32.0/19130.9.32.1 to 130.9.63.254130.9.63.2558,190
75130.9.64.0/19130.9.64.1 to 130.9.95.254130.9.95.2558,190
76130.9.96.0/19130.9.96.1 to 130.9.127.254130.9.127.2558,190
77130.9.128.0/19130.9.128.1 to 130.9.159.254130.9.159.2558,190
78130.9.160.0/19130.9.160.1 to 130.9.191.254130.9.191.2558,190
79130.9.192.0/19130.9.192.1 to 130.9.223.254130.9.223.2558,190
80130.9.224.0/19130.9.224.1 to 130.9.255.254130.9.255.2558,190
81130.10.0.0/19130.10.0.1 to 130.10.31.254130.10.31.2558,190
82130.10.32.0/19130.10.32.1 to 130.10.63.254130.10.63.2558,190
83130.10.64.0/19130.10.64.1 to 130.10.95.254130.10.95.2558,190
84130.10.96.0/19130.10.96.1 to 130.10.127.254130.10.127.2558,190
85130.10.128.0/19130.10.128.1 to 130.10.159.254130.10.159.2558,190
86130.10.160.0/19130.10.160.1 to 130.10.191.254130.10.191.2558,190
87130.10.192.0/19130.10.192.1 to 130.10.223.254130.10.223.2558,190
88130.10.224.0/19130.10.224.1 to 130.10.255.254130.10.255.2558,190
89130.11.0.0/19130.11.0.1 to 130.11.31.254130.11.31.2558,190
90130.11.32.0/19130.11.32.1 to 130.11.63.254130.11.63.2558,190
91130.11.64.0/19130.11.64.1 to 130.11.95.254130.11.95.2558,190
92130.11.96.0/19130.11.96.1 to 130.11.127.254130.11.127.2558,190
93130.11.128.0/19130.11.128.1 to 130.11.159.254130.11.159.2558,190
94130.11.160.0/19130.11.160.1 to 130.11.191.254130.11.191.2558,190
95130.11.192.0/19130.11.192.1 to 130.11.223.254130.11.223.2558,190
96130.11.224.0/19130.11.224.1 to 130.11.255.254130.11.255.2558,190
97130.12.0.0/19130.12.0.1 to 130.12.31.254130.12.31.2558,190
98130.12.32.0/19130.12.32.1 to 130.12.63.254130.12.63.2558,190
99130.12.64.0/19130.12.64.1 to 130.12.95.254130.12.95.2558,190
100130.12.96.0/19130.12.96.1 to 130.12.127.254130.12.127.2558,190
101130.12.128.0/19130.12.128.1 to 130.12.159.254130.12.159.2558,190
102130.12.160.0/19130.12.160.1 to 130.12.191.254130.12.191.2558,190
103130.12.192.0/19130.12.192.1 to 130.12.223.254130.12.223.2558,190
104130.12.224.0/19130.12.224.1 to 130.12.255.254130.12.255.2558,190
105130.13.0.0/19130.13.0.1 to 130.13.31.254130.13.31.2558,190
106130.13.32.0/19130.13.32.1 to 130.13.63.254130.13.63.2558,190
107130.13.64.0/19130.13.64.1 to 130.13.95.254130.13.95.2558,190
108130.13.96.0/19130.13.96.1 to 130.13.127.254130.13.127.2558,190
109130.13.128.0/19130.13.128.1 to 130.13.159.254130.13.159.2558,190
110130.13.160.0/19130.13.160.1 to 130.13.191.254130.13.191.2558,190
111130.13.192.0/19130.13.192.1 to 130.13.223.254130.13.223.2558,190
112130.13.224.0/19130.13.224.1 to 130.13.255.254130.13.255.2558,190
113130.14.0.0/19130.14.0.1 to 130.14.31.254130.14.31.2558,190
114130.14.32.0/19130.14.32.1 to 130.14.63.254130.14.63.2558,190
115130.14.64.0/19130.14.64.1 to 130.14.95.254130.14.95.2558,190
116130.14.96.0/19130.14.96.1 to 130.14.127.254130.14.127.2558,190
117130.14.128.0/19130.14.128.1 to 130.14.159.254130.14.159.2558,190
118130.14.160.0/19130.14.160.1 to 130.14.191.254130.14.191.2558,190
119130.14.192.0/19130.14.192.1 to 130.14.223.254130.14.223.2558,190
120130.14.224.0/19130.14.224.1 to 130.14.255.254130.14.255.2558,190
121130.15.0.0/19130.15.0.1 to 130.15.31.254130.15.31.2558,190
122130.15.32.0/19130.15.32.1 to 130.15.63.254130.15.63.2558,190
123130.15.64.0/19130.15.64.1 to 130.15.95.254130.15.95.2558,190
124130.15.96.0/19130.15.96.1 to 130.15.127.254130.15.127.2558,190
125130.15.128.0/19130.15.128.1 to 130.15.159.254130.15.159.2558,190
126130.15.160.0/19130.15.160.1 to 130.15.191.254130.15.191.2558,190
127130.15.192.0/19130.15.192.1 to 130.15.223.254130.15.223.2558,190
128130.15.224.0/19130.15.224.1 to 130.15.255.254130.15.255.2558,190
129130.16.0.0/19130.16.0.1 to 130.16.31.254130.16.31.2558,190
130130.16.32.0/19130.16.32.1 to 130.16.63.254130.16.63.2558,190
131130.16.64.0/19130.16.64.1 to 130.16.95.254130.16.95.2558,190
132130.16.96.0/19130.16.96.1 to 130.16.127.254130.16.127.2558,190
133130.16.128.0/19130.16.128.1 to 130.16.159.254130.16.159.2558,190
134130.16.160.0/19130.16.160.1 to 130.16.191.254130.16.191.2558,190
135130.16.192.0/19130.16.192.1 to 130.16.223.254130.16.223.2558,190
136130.16.224.0/19130.16.224.1 to 130.16.255.254130.16.255.2558,190
137130.17.0.0/19130.17.0.1 to 130.17.31.254130.17.31.2558,190
138130.17.32.0/19130.17.32.1 to 130.17.63.254130.17.63.2558,190
139130.17.64.0/19130.17.64.1 to 130.17.95.254130.17.95.2558,190
140130.17.96.0/19130.17.96.1 to 130.17.127.254130.17.127.2558,190
141130.17.128.0/19130.17.128.1 to 130.17.159.254130.17.159.2558,190
142130.17.160.0/19130.17.160.1 to 130.17.191.254130.17.191.2558,190
143130.17.192.0/19130.17.192.1 to 130.17.223.254130.17.223.2558,190
144130.17.224.0/19130.17.224.1 to 130.17.255.254130.17.255.2558,190
145130.18.0.0/19130.18.0.1 to 130.18.31.254130.18.31.2558,190
146130.18.32.0/19130.18.32.1 to 130.18.63.254130.18.63.2558,190
147130.18.64.0/19130.18.64.1 to 130.18.95.254130.18.95.2558,190
148130.18.96.0/19130.18.96.1 to 130.18.127.254130.18.127.2558,190
149130.18.128.0/19130.18.128.1 to 130.18.159.254130.18.159.2558,190
150130.18.160.0/19130.18.160.1 to 130.18.191.254130.18.191.2558,190
151130.18.192.0/19130.18.192.1 to 130.18.223.254130.18.223.2558,190
152130.18.224.0/19130.18.224.1 to 130.18.255.254130.18.255.2558,190
153130.19.0.0/19130.19.0.1 to 130.19.31.254130.19.31.2558,190
154130.19.32.0/19130.19.32.1 to 130.19.63.254130.19.63.2558,190
155130.19.64.0/19130.19.64.1 to 130.19.95.254130.19.95.2558,190
156130.19.96.0/19130.19.96.1 to 130.19.127.254130.19.127.2558,190
157130.19.128.0/19130.19.128.1 to 130.19.159.254130.19.159.2558,190
158130.19.160.0/19130.19.160.1 to 130.19.191.254130.19.191.2558,190
159130.19.192.0/19130.19.192.1 to 130.19.223.254130.19.223.2558,190
160130.19.224.0/19130.19.224.1 to 130.19.255.254130.19.255.2558,190
161130.20.0.0/19130.20.0.1 to 130.20.31.254130.20.31.2558,190
162130.20.32.0/19130.20.32.1 to 130.20.63.254130.20.63.2558,190
163130.20.64.0/19130.20.64.1 to 130.20.95.254130.20.95.2558,190
164130.20.96.0/19130.20.96.1 to 130.20.127.254130.20.127.2558,190
165130.20.128.0/19130.20.128.1 to 130.20.159.254130.20.159.2558,190
166130.20.160.0/19130.20.160.1 to 130.20.191.254130.20.191.2558,190
167130.20.192.0/19130.20.192.1 to 130.20.223.254130.20.223.2558,190
168130.20.224.0/19130.20.224.1 to 130.20.255.254130.20.255.2558,190
169130.21.0.0/19130.21.0.1 to 130.21.31.254130.21.31.2558,190
170130.21.32.0/19130.21.32.1 to 130.21.63.254130.21.63.2558,190
171130.21.64.0/19130.21.64.1 to 130.21.95.254130.21.95.2558,190
172130.21.96.0/19130.21.96.1 to 130.21.127.254130.21.127.2558,190
173130.21.128.0/19130.21.128.1 to 130.21.159.254130.21.159.2558,190
174130.21.160.0/19130.21.160.1 to 130.21.191.254130.21.191.2558,190
175130.21.192.0/19130.21.192.1 to 130.21.223.254130.21.223.2558,190
176130.21.224.0/19130.21.224.1 to 130.21.255.254130.21.255.2558,190
177130.22.0.0/19130.22.0.1 to 130.22.31.254130.22.31.2558,190
178130.22.32.0/19130.22.32.1 to 130.22.63.254130.22.63.2558,190
179130.22.64.0/19130.22.64.1 to 130.22.95.254130.22.95.2558,190
180130.22.96.0/19130.22.96.1 to 130.22.127.254130.22.127.2558,190
181130.22.128.0/19130.22.128.1 to 130.22.159.254130.22.159.2558,190
182130.22.160.0/19130.22.160.1 to 130.22.191.254130.22.191.2558,190
183130.22.192.0/19130.22.192.1 to 130.22.223.254130.22.223.2558,190
184130.22.224.0/19130.22.224.1 to 130.22.255.254130.22.255.2558,190
185130.23.0.0/19130.23.0.1 to 130.23.31.254130.23.31.2558,190
186130.23.32.0/19130.23.32.1 to 130.23.63.254130.23.63.2558,190
187130.23.64.0/19130.23.64.1 to 130.23.95.254130.23.95.2558,190
188130.23.96.0/19130.23.96.1 to 130.23.127.254130.23.127.2558,190
189130.23.128.0/19130.23.128.1 to 130.23.159.254130.23.159.2558,190
190130.23.160.0/19130.23.160.1 to 130.23.191.254130.23.191.2558,190
191130.23.192.0/19130.23.192.1 to 130.23.223.254130.23.223.2558,190
192130.23.224.0/19130.23.224.1 to 130.23.255.254130.23.255.2558,190
193130.24.0.0/19130.24.0.1 to 130.24.31.254130.24.31.2558,190
194130.24.32.0/19130.24.32.1 to 130.24.63.254130.24.63.2558,190
195130.24.64.0/19130.24.64.1 to 130.24.95.254130.24.95.2558,190
196130.24.96.0/19130.24.96.1 to 130.24.127.254130.24.127.2558,190
197130.24.128.0/19130.24.128.1 to 130.24.159.254130.24.159.2558,190
198130.24.160.0/19130.24.160.1 to 130.24.191.254130.24.191.2558,190
199130.24.192.0/19130.24.192.1 to 130.24.223.254130.24.223.2558,190
200130.24.224.0/19130.24.224.1 to 130.24.255.254130.24.255.2558,190
201130.25.0.0/19130.25.0.1 to 130.25.31.254130.25.31.2558,190
202130.25.32.0/19130.25.32.1 to 130.25.63.254130.25.63.2558,190
203130.25.64.0/19130.25.64.1 to 130.25.95.254130.25.95.2558,190
204130.25.96.0/19130.25.96.1 to 130.25.127.254130.25.127.2558,190
205130.25.128.0/19130.25.128.1 to 130.25.159.254130.25.159.2558,190
206130.25.160.0/19130.25.160.1 to 130.25.191.254130.25.191.2558,190
207130.25.192.0/19130.25.192.1 to 130.25.223.254130.25.223.2558,190
208130.25.224.0/19130.25.224.1 to 130.25.255.254130.25.255.2558,190
209130.26.0.0/19130.26.0.1 to 130.26.31.254130.26.31.2558,190
210130.26.32.0/19130.26.32.1 to 130.26.63.254130.26.63.2558,190
211130.26.64.0/19130.26.64.1 to 130.26.95.254130.26.95.2558,190
212130.26.96.0/19130.26.96.1 to 130.26.127.254130.26.127.2558,190
213130.26.128.0/19130.26.128.1 to 130.26.159.254130.26.159.2558,190
214130.26.160.0/19130.26.160.1 to 130.26.191.254130.26.191.2558,190
215130.26.192.0/19130.26.192.1 to 130.26.223.254130.26.223.2558,190
216130.26.224.0/19130.26.224.1 to 130.26.255.254130.26.255.2558,190
217130.27.0.0/19130.27.0.1 to 130.27.31.254130.27.31.2558,190
218130.27.32.0/19130.27.32.1 to 130.27.63.254130.27.63.2558,190
219130.27.64.0/19130.27.64.1 to 130.27.95.254130.27.95.2558,190
220130.27.96.0/19130.27.96.1 to 130.27.127.254130.27.127.2558,190
221130.27.128.0/19130.27.128.1 to 130.27.159.254130.27.159.2558,190
222130.27.160.0/19130.27.160.1 to 130.27.191.254130.27.191.2558,190
223130.27.192.0/19130.27.192.1 to 130.27.223.254130.27.223.2558,190
224130.27.224.0/19130.27.224.1 to 130.27.255.254130.27.255.2558,190
225130.28.0.0/19130.28.0.1 to 130.28.31.254130.28.31.2558,190
226130.28.32.0/19130.28.32.1 to 130.28.63.254130.28.63.2558,190
227130.28.64.0/19130.28.64.1 to 130.28.95.254130.28.95.2558,190
228130.28.96.0/19130.28.96.1 to 130.28.127.254130.28.127.2558,190
229130.28.128.0/19130.28.128.1 to 130.28.159.254130.28.159.2558,190
230130.28.160.0/19130.28.160.1 to 130.28.191.254130.28.191.2558,190
231130.28.192.0/19130.28.192.1 to 130.28.223.254130.28.223.2558,190
232130.28.224.0/19130.28.224.1 to 130.28.255.254130.28.255.2558,190
233130.29.0.0/19130.29.0.1 to 130.29.31.254130.29.31.2558,190
234130.29.32.0/19130.29.32.1 to 130.29.63.254130.29.63.2558,190
235130.29.64.0/19130.29.64.1 to 130.29.95.254130.29.95.2558,190
236130.29.96.0/19130.29.96.1 to 130.29.127.254130.29.127.2558,190
237130.29.128.0/19130.29.128.1 to 130.29.159.254130.29.159.2558,190
238130.29.160.0/19130.29.160.1 to 130.29.191.254130.29.191.2558,190
239130.29.192.0/19130.29.192.1 to 130.29.223.254130.29.223.2558,190
240130.29.224.0/19130.29.224.1 to 130.29.255.254130.29.255.2558,190
241130.30.0.0/19130.30.0.1 to 130.30.31.254130.30.31.2558,190
242130.30.32.0/19130.30.32.1 to 130.30.63.254130.30.63.2558,190
243130.30.64.0/19130.30.64.1 to 130.30.95.254130.30.95.2558,190
244130.30.96.0/19130.30.96.1 to 130.30.127.254130.30.127.2558,190
245130.30.128.0/19130.30.128.1 to 130.30.159.254130.30.159.2558,190
246130.30.160.0/19130.30.160.1 to 130.30.191.254130.30.191.2558,190
247130.30.192.0/19130.30.192.1 to 130.30.223.254130.30.223.2558,190
248130.30.224.0/19130.30.224.1 to 130.30.255.254130.30.255.2558,190
249130.31.0.0/19130.31.0.1 to 130.31.31.254130.31.31.2558,190
250130.31.32.0/19130.31.32.1 to 130.31.63.254130.31.63.2558,190
251130.31.64.0/19130.31.64.1 to 130.31.95.254130.31.95.2558,190
252130.31.96.0/19130.31.96.1 to 130.31.127.254130.31.127.2558,190
253130.31.128.0/19130.31.128.1 to 130.31.159.254130.31.159.2558,190
254130.31.160.0/19130.31.160.1 to 130.31.191.254130.31.191.2558,190
255130.31.192.0/19130.31.192.1 to 130.31.223.254130.31.223.2558,190
256130.31.224.0/19130.31.224.1 to 130.31.255.254130.31.255.2558,190

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.